It is hard to say which (investment or consumption) is more important than the other given that both are crucial process for one economy from which they are interdependent. Without domestic consumptions, firms would not invest in new factories if they do not make any returns (the rates of return); on the other hand, if there is no investment on our economy, the economy simply goes bust ( remember the concept of depreciation).
It is more appropriate to rephrase your question and ask if ‘investment-led economic growth (Asian style followed by Japan, four dragons and China) or consumption-led economic growth (America) is better than the other?